Also maybe useful info for others. I have decided to go little bit different way in the end. Since next version will be in Locus three versions of MapsForge library .

- quite old for maps version V2- heavily modified and optimized library for all maps V3 (LoMaps and most of current maps) that will also work with themes version 1, 2, 3, will offer auto-loading and work with LoMaps Poi DB- current unmodified version of MapsForge library (currently version 0.6, maps V4) that will work only with map themes version 4, no autoloading, no POI Db

So for maps V3, only themes with version="1, 2, 3", for maps V4, themes with version="4".

Hm, that's a bit strict. There's no issue in using V3 maps with V4 themes. Although the numbers differ, they aren't dependent on each other. Mapsforge 0.5 introduced V4 themes, while still producing V3 maps. It would be strange to be able to install V4 themes but not to use them, and will certainly cause support issues.

So if you install and choose a V4 theme switching to standard mapsforge would make sense to me.

Locus is the only game in town. For simple navigation maybe another apps are suitable, but if you hike with small children, or hike so actively that need to manage your tracks and display on the map, Locus is the only choice for now (I have tried a lot of apps, and bought Android smartphone specially for navigation because Locus not available for iOS).

But problem is that default theme is not so good as Elevate from @Tobias. I have tried to file issues (https://help.locusmap.eu/topic/bench-symbol-is-not-displayed-internal-hikebike-theme), but Elevate has not only minor advantages, but a major advantages also (e.g. compare presentation of cable car near Mittenwald (Germany) — Locus theme doesn't render cable car name opposite to Elevate, so, I have to guess what is this).

So, even if I buy LoMaps (to financially support Locus development), I don't use it. Because as far I understand (and I as far I experienced) for Elevate themes better to use openandromaps.

And now Tobias announced that "OpenAndroMaps will switch to Multilanguage “V4” Maps mid of 2019.". And stated that "The ony real disadvantage over V3 maps, as I know, is that Locus does not support automatic map switching with V4 maps." (because Locus will use not optimised mapsforge engine to render V4 maps). But from this topic I see that maybe will number of other issues. Or it is fixed now?